Lung cancer claims approximately 150,000 lives each year in the USA and its incidence is increasing globally. Early diagnosis of this disease is difficult to obtain. The five-year survival rate of patients with lung cancer is approximately 14 percent and has not changed over the past several decades. The purpose of the proposed research is to establish the potential of the thymidine analog 5-iodo-2'-deoxyuridine (IUdR) radiolabeled with the gamma-emitting isotope iodine-123 (I-123) for the scintigraphic detection of lung cancer and radiolabeled with either the Auger electron-emitting isotope iodine-125 or the beta-emitting isotope iodine-131 for the therapy of lung cancer. To this end, experiments have been designed to examine the specific uptake of radiolabeled IUdR in nude mice bearing cancer cells growing within the lungs. The approaches described should provide an opportunity for the selective targeting of dividing cancerous cells within the lungs and lead to methods for scintigraphic detection of lung cancer as well as development of an effective/adjuvant therapeutic approach.